MotoMojo: Ethanol in Gasoline

Oct 22, 2014 View Comments by

MotoMojo: Ethanol in GasolineMost motorcyclists are affected by the ethanol mixed in their gasoline, whether they know it or not. Ethanol is a type of alcohol produced by fermentation of various food stocks and subsequent distillation. About 95 percent of U.S. ethanol comes from corn.

Gasoline has evolved into reformulated blends over the years due to numerous laws. California completely outlawed the use of lead in automotive fuels in 1992. Later in 1996, the Golden State regulated aromatics, benzene, sulfur, oxygenates, and other hydrocarbons. Then in 1999, new reformulated gasolines were introduced, and methyl-tertiary-butyl-ether (MTBE) was banned. MTBE improved octane and combustion but was found to create environmental problems when it got into the groundwater, etc. The EPA and other states introduced similar regulations.

Ethanol was introduced as a gasoline additive following the phase out of MTBE. For about the last 15 years, ethanol has been approved by the Environmental Protection Agency (EPA) to be added to gasoline up to 10 percent, which is known as E10. Recently E15 (15 percent ethanol, 85 percent gasoline) was approved for sale. Although the EPA has approved E15 for use in 2001 and newer light-duty vehicles, which include most cars, light-duty trucks, and SUVS, the agency has not approved the use of E15 in motorcycles or ATVs. Fuel containing 85 percent ethanol and 15 percent gasoline is sold in some filling stations (called E-85) for use in flexible-fuel vehicles specially designed to adapt to various mixtures but definitely not for use in motorcycles either. Motorcyclists should avoid refueling from “blender” pumps, which dispense both E10 and E15 from the same hose, as residual E15 may remain in the hose.

MotoMojo: Ethanol in GasolinePure gasoline doesn’t contain oxygen, so “oxygenates” such as MTBE and ethanol were introduced to fuel to deliver extra oxygen into the combustion process. Oxygenates allow engines with excessively rich air-fuel mixtures (mainly found in carbureted engines) to more completely burn their fuel, resulting in less-toxic exhaust gases. It also serves to “stretch” the volume of gasoline and reduce fuel imports.

However, ethanol production has raised the price of corn, with economic ripple effects that increased the cost of raising livestock and other foods. Ethanol contains about 30 percent less energy than gasoline by volume. With E10 fuel, which is found in more than 90 percent of automotive gasoline sold in the U.S., fuel economy is about 3 percent lower than with straight gasoline.

Alcohol is hygroscopic, which means it absorbs moisture from its surroundings, in this case mainly condensation from air above the fuel. When the absorbed moisture reaches a critical percentage, phase separation occurs, resulting in the alcohol dropping out of the mixture and sinking to the bottom of the tank. Phase separation can also lead to the formation of a slime, which sticks to the walls of the tank and fuel system. If it dries, it may leave insoluble hard deposits throughout the system, clogging jets and orifices and jamming electric pumps.

MotoMojo: Ethanol in GasolineEthanol and water can make formic acid, and cause galvanic corrosion. Metals, plastics, and rubber parts in the fuel system are subject to deterioration and corrosion. Combined with additional heat from running lean, this can eventually damage the engine, fuel lines, tank, and exhaust.
Abrasive aluminum oxide, a white gritty powder, can form and settle in float chambers and other aluminum fuel system parts such as filter housings and pumps. When drawn into the engine, it can cause extensive damage.

Older motorcycles were not constructed with corrosion-resistant fuel systems nor can they tolerate the higher combustion temperatures that occur when E10 is burned. That’s because the oxygenates cause a leaner air-fuel mixture, which may overheat valves or pistons. Fuel hoses should be replaced more often, and pre-2000 models should have all rubber fuel parts upgraded to be compatible with modern gasolines. Vintage engines should be fitted with hardened valve seats.
Ethanol-laced gasoline deteriorates more quickly and forms gums and residues that may prevent fuel from flowing properly, especially though carburetor jets and passages. Older model motorcycles are particularly hard hit by this, and many bikes won’t start or will run very poorly after sitting for several months. Typically the engine may barely start, run poorly, and then stall if the choke is opened.

Two-stroke motorcycles are especially vulnerable to ethanol-laced fuels; alcohol reduces the lubricity of the fuel-oil mixture and may lead to piston sticking and engine seizure. Older motorcycles with fiberglass or plastic gas tanks are subject to tank swelling, leakage, or failure. Many additives have been developed to counter the negative effects of ethanol in gasoline, but some of alcohol’s effects can’t be eliminated. Therefore, straight gasoline should be purchased where available.

Motorcycles are often parked for extended periods, and vehicles that aren’t used regularly are most susceptible to ethanol-related problems. Fuel stabilizer should be added, which can slow deterioration and corrosive effects. However, additives can’t reverse phase separation. Owners should make sure the gas tank is topped off (with fresh gas) so there’s little air above the fuel to introduce moisture. RR

Visit to help protect your motorcycle from E15. To locate ethanol-free gas stations near you, visit

By Ken Freund

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